In the related art, an image forming apparatus includes a fixing device which is able to change a pressure of a pressure roller that comes in contact with a heat roller in a step-wise manner. By changing the pressure of the pressure roller, it is possible to modulate the heating amount applied to a recording medium.
When changing the pressure of the pressure roller, the pressure roller is separated from the heat roller, and the inter-axle distance between the pressure roller and the heat roller changes slightly. In a state in which the pressure roller is brought into contact with the heat roller, the pressure roller is pressed toward the heat roller by a spring or the like.
In the standby state in which recording media are not fed, the pressure roller is moved to a separation position not contacting the heat roller. Therefore, a mechanical operation sound is generated when the pressure roller is moved from the contact position to the separation position. In order to ensure the fixing capability in a color copy machine or the like with a high paper feed speed, the pressure applied by the pressure roller is set comparatively large. Thus, the load fluctuation between when contacting and when separating is large, and the operation sound is loud when the pressure roller is separated from the heat roller.
Thus, there is demand for the development of an image forming apparatus in which the operation sound of the fixing device is low.